Golapkar, who was standing near the door of the women's compartment, fell out, hitting her head on a railway pole.
The accused then fled with her earrings, gold chain and purse, collectively worth Rs. 26,000, the police said.
According to the government railway police (GRP) at Vashi, Golapkar had boarded the 7.28pm train at Kopar Khairane to get to her Dombivli residence via Thane. "We have detained one suspect and are questioning him," said PM Karyakarte, senior inspector, Vashi GRP.
Golapkar, who has sustained grievous head and hip injuries, is admitted to Criticare Hospital in Thane.